The most important buffering system in the body is which of the following?

The most important buffering system in the body is which of the following?

• A. Hemoglobin
• B. Plasma proteins
• C. Bone
• D. [HCO3-]

Answer: (D)

The bicarbonate buffering system is the primary mechanism for maintaining blood pH. In extracellular fluid, carbon dioxide from metabolism combines with water to form carbonic acid, which quickly dissociates into hydrogen ions and bicarbonate. The pH is governed by the ratio of bicarbonate to dissolved CO2 (pH = pKa + log([HCO3-]/(0.03×Pco2)); the pKa of carbonic acid is about 6.1), so small changes in this ratio produce big shifts in pH. The lungs rapidly control CO2 levels by adjusting ventilation, while the kidneys regulate bicarbonate reabsorption and generation, providing long-term adjustment. Other buffers, like hemoglobin in red blood cells and plasma proteins, contribute as well but to a lesser extent in the overall buffering capacity. Bone acts as a slow reservoir and does not drive acute acid-base balance.

The bicarbonate buffering system is the primary mechanism for maintaining blood pH. In extracellular fluid, carbon dioxide from metabolism combines with water to form carbonic acid, which quickly dissociates into hydrogen ions and bicarbonate. The pH is governed by the ratio of bicarbonate to dissolved CO2 (pH = pKa + log([HCO3-]/(0.03×Pco2)); the pKa of carbonic acid is about 6.1), so small changes in this ratio produce big shifts in pH. The lungs rapidly control CO2 levels by adjusting ventilation, while the kidneys regulate bicarbonate reabsorption and generation, providing long-term adjustment. Other buffers, like hemoglobin in red blood cells and plasma proteins, contribute as well but to a lesser extent in the overall buffering capacity. Bone acts as a slow reservoir and does not drive acute acid-base balance.